Updated: Tuesday, August 14th, 2018 at 9:17pm

SANTA FE – Gary Johnson is embarking on a new adventure – a late entrance into a U.S. Senate race that features two other candidates who have been campaigning for months.

The former New Mexico governor, a Republican-turned-Libertarian, is expected to formally announce his campaign later this week. But the necessary paperwork was filed late Monday with the Secretary of State’s Office for Johnson to appear on the Nov. 6 ballot.

“Gov. Johnson is obviously taking the necessary steps to be a candidate for U.S. Senate, and today’s filing is one of those steps,” his longtime communications director, Joe Hunter, told the Journal.

Ex-Gov. Gary Johnson

Johnson, a Taos resident, was a Republican when he served as governor from 1995 through 2002. He later switched his party affiliation to Libertarian and ran for president in 2012 and 2016.

His return to New Mexico politics could not only shake up the Senate race – the other candidates are incumbent Democrat Martin Heinrich and Republican Mick Rich – but might also help other Libertarian candidates on the ballot.

Libertarians have major-party status for this year’s state election cycle, largely because Johnson received 9.3 percent of the New Mexico votes in the 2016 general election. However, no Libertarian has ever won election to the U.S. Senate, and Johnson will likely face an uphill battle despite his name recognition.

Heinrich’s re-election campaign circulated a memo Tuesday that highlighted some of Johnson’s past policy positions – including repealing the federal Affordable Care Act and raising the age for Social Security retirement eligibility to at least 70 and possibly higher.

“New Mexicans want someone who has fought for them each and every day, and that’s why I’m running on my record and my vision for our state,” Heinrich said in a statement.

State Democratic Party Chairwoman Marg Elliston also released a statement in which she described Johnson’s policy positions as “extreme.”

Meanwhile, a campaign spokesman for Rich, an Albuquerque contractor who faced no opposition in the Republican primary, blasted both Johnson and Heinrich as “career politicians.” Rich’s campaign also said Johnson would siphon votes from Heinrich.

Johnson vowed after his 2016 presidential bid that he was done with political races, but he reconsidered his stance in recent months at the urging of New Mexico Libertarians. Party insiders nominated him earlier this month to replace state Land Commissioner Aubrey Dunn on the general election ballot.

As Johnson considered a potential run, an independent political committee called Elect Liberty PAC was formed to help raise money for his possible campaign.

“He’s fiscally conservative and socially cool,” said the ad, which Johnson tweeted.

A businessman before he got into politics, Johnson created waves – and opposition from some other Republicans – as governor in 1999 when he publicly advocated for the legalization of drugs, including marijuana. In addition, his propensity for vetoing bills passed by the Democratic-controlled Legislature earned him the nickname “Governor No.”

An avid skier and triathlete, Johnson recently completed a 2,800-mile Continental Divide bike race – from the town of Banff, Alberta, in the Canadian Rockies, to the Mexican border at Antelope Wells.